Ablation of myocardial tissue is well known as a treatment for cardiac arrhythmias. In radio-frequency (RF) ablation, for example, a catheter is inserted into the heart and brought into contact with tissue at a target location. RF energy is then applied through electrodes on the catheter in order to create a lesion for the purpose of breaking arrhythmogenic current paths in the tissue.
Irrigated catheters are now commonly used in ablation procedures. Irrigation provides many benefits including cooling of the electrode and tissue which prevents overheating of tissue that can otherwise cause the formation of char and coagulum and even steam pops. However, because tissue temperature is assessed during an ablation procedure to avoid such adverse occurrences, it is important that the temperature sensed accurately reflects the real temperature of the tissue and not merely the surface temperature of the tissue which can be biased by the cooling irrigation fluid from the catheter. Moreover, deeper tissue contact in general provides more accurate thermal and electrical readings, including improved impedance measurements for purposes, including a determination of lesion size, depth and transmurality.
Accordingly, there is a desire for an irrigated ablation catheter with a distal end that can better probe tissue without significantly damaging or breaching the tissue, for more accurate measurements, including temperature sensing and impedance measurements.
Additionally, excessive pressure at the tip of the irrigated ablation, however, may cause undesired damage to the tissue, particularly to heart tissue and may even perforate the heart wall.
For example, in intracardiac radio-frequency (RF) ablation, a catheter having an electrode at its distal tip is inserted through the patient's vascular system into a chamber of the heart. The electrode is brought into contact with a site (or sites) on the endocardium, and RF energy is applied through the catheter to the electrode in order to ablate the heart tissue at the site. Proper contact between the electrode and the endocardium during ablation is necessary in order to achieve the desired therapeutic effect without excessive damage to the tissue